1. Field of the Invention
The present invention relates to a technology for using a plurality of communication chips performing isochronous transfer to increase a number of isochronous stream transfers.
2. Description of the Related Art
The IEEE 1394 standard specifies a communication protocol including a physical layer for performing signal input/output from/to a bus, a data link layer for performing isochronous transfer and asynchronous transfer using the physical layer, and a transaction layer for performing upper-layer data transfer using the asynchronous transfer of the data link layer.
A communication chip for IEEE 1394 in charge of the processing for the physical and data link layers is known (see, for example, Japanese Unexamined Patent Application Publication No. 10-285223).
A communication chip such as the chip described above has restrictions on a number of isochronous stream transfers which can simultaneously be preformed. One way to increase the number of simultaneous isochronous stream transfers is to use a plurality of communication chips. However, this causes a problem in that since each of the node IDs, which are the IDs of respective devices in the network, is assigned to a physical layer implemented in each of the communication chips, isochronous transfers using a plurality of communication chips are unfavorably recognized as independent transfers performed by different nodes corresponding to the different communication chips. In addition, various processes at layers above the data link layer required for isochronous transfer need to be performed for each node ID.